Poster to presented at 193rd AAS meeting in Austin, Texas on 5-9 January 1999:

An Investigation of the Performance of CCD Stellar Photometry
with a 1.5-micron Diffraction-Limited 8-m Next Generation Space Telescope

Kenneth J. Mighell (KPNO/NOAO)

ABSTRACT:

I present the results of an investigation of the performance of CCD stellar
photometry with a 1.5-micron diffraction-limited 8-m Next Generation
Space Telescope. These simulations used artificial Point Spread Functions
for three different 8-m NGST design concepts which were kindly provided
by John Krist. Assuming that the 8-m NGST primary mirror has 1/13
wave RMS errors at 1.5 micron, I demonstrate that 90% of the light from
a star falls within an aperture radius of 0.1 arcsec --- the size of one
WF pixel of the Hubble Space Telescope WFPC2 instrument. The three
NGST design concepts have nearly identical V-band encircled-energy
functions; the degradation caused by the differences between the different
design concepts is quite negligible when state-of-the-art digital-PSF
photometric reduction software is used to analyze uncrowded stellar
fields. All the V-band PSFs used in these simulations were sampled at
0.0064 arcsec/pixel which is the critical V-band sampling rate
of a perfect 0.5-micron diffraction-limited 8-m NGST. Better
photometric performance for all three NGST design concepts could
be obtained by using larger CCD pixels: a pixel size of ~0.013
(~2 x 0.0064) arcsec/pixel should provide an optimal
pixel sampling when the 8-m primary mirror is diffraction-limited at
1.5 micron.